RSV vaccines are highly effective, reducing serious lung infections by roughly 70% to 82% depending on the vaccine, the population, and how much time has passed since vaccination. Three RSV vaccines are now available in the United States, each targeting a different group: older adults, pregnant people (to protect newborns), or young children. Here’s what the numbers actually look like.
Effectiveness in Older Adults
For adults 60 and older, a single dose of the GSK vaccine (Arexvy) reduced RSV-related lower respiratory tract disease by about 75% over its first two seasons of clinical trial data. When researchers adjusted for seasonal variation, that number settled closer to 67%. These are strong results for a respiratory vaccine, particularly in an older population where immune responses tend to be weaker.
Real-world data has been even more encouraging than the clinical trials suggested. A study tracking vaccinated older adults in routine medical settings found the vaccine was 92% effective at preventing emergency department visits and hospitalizations from RSV among people with chronic health conditions. Among adults 75 and older specifically, effectiveness reached 95%. Protection against the most severe outcomes, including ICU admission and mechanical ventilation, was around 90%.
The vast majority of people in that real-world study (nearly 93%) had at least one chronic condition. Almost half had COPD, and more than 14% had weakened immune systems. The fact that the vaccine still performed well in this sicker-than-average group is reassuring, since these are exactly the people most likely to end up hospitalized from RSV.
Who Should Get Vaccinated
The CDC recommends an RSV vaccine for all adults 75 and older. Adults between 50 and 74 are also recommended to get vaccinated if they have conditions that raise their risk of severe RSV illness. Those conditions include chronic heart or lung disease (such as heart failure, COPD, or asthma), a weakened immune system, diabetes with organ damage, severe obesity (BMI of 40 or higher), chronic liver or kidney disease, neurological conditions that affect breathing or swallowing, sickle cell disease, and living in a nursing home. Only a single dose is currently recommended.
Protection for Newborns
RSV is one of the leading causes of hospitalization in infants, and babies are too young to be vaccinated themselves in the first months of life. The Pfizer vaccine (Abrysvo) addresses this by vaccinating pregnant people during the third trimester, allowing protective antibodies to cross the placenta before birth.
In clinical trials, this approach was 82% effective at preventing severe RSV lung disease in infants during their first 90 days of life. By six months, protection had declined somewhat but remained substantial at about 69%. That early window of strongest protection aligns with the period when infants are most vulnerable to severe RSV complications.
How Long Protection Lasts
One important limitation of RSV vaccines is that protection does fade over time. In the GSK clinical trial, efficacy against lower respiratory tract disease dropped from about 75% in the first season to roughly 67% when measured across two full seasons. That decline is meaningful but modest, and the vaccine still offered substantial protection well into the second year.
For now, the CDC recommends only a single dose for adults rather than annual boosters. Whether a second dose will eventually be recommended, and how far apart doses should be spaced, remains an open question as more data accumulates.
Safety and Side Effects
The most common side effects of RSV vaccines are what you’d expect from any vaccination: soreness at the injection site, fatigue, headache, and muscle pain. These are generally mild and resolve within a few days.
The more notable safety concern involves Guillain-Barré syndrome (GBS), a rare neurological condition where the immune system attacks nerve cells, causing weakness and sometimes temporary paralysis. The FDA now requires a GBS warning on both the Arexvy and Abrysvo labels. Analysis of insurance claims data estimated roughly 7 to 9 excess cases of GBS per million doses administered in adults 65 and older during the 42 days following vaccination. To put that in perspective, that’s fewer than 1 in 100,000 vaccinated people. GBS is also a known rare complication of several other vaccines and of RSV infection itself.
For most older adults, particularly those with chronic conditions that put them at high risk for severe RSV, the benefit of preventing hospitalization and ICU stays substantially outweighs this small risk. The calculus is less clear-cut for healthy adults in their 50s and 60s, which is part of why the CDC limits its routine recommendation to those 75 and older or those with specific risk factors.
Comparing the Available Vaccines
Three RSV vaccines are currently approved in the U.S. for adults: Arexvy (GSK), Abrysvo (Pfizer), and mRESVIA (Moderna). Arexvy and Abrysvo are protein-based vaccines, while mRESVIA uses mRNA technology similar to some COVID-19 vaccines. All three target the same key protein on the surface of the RSV virus.
The clinical trial designs differed enough that direct head-to-head efficacy comparisons aren’t reliable, but all three demonstrated strong protection against RSV-related lower respiratory tract disease in older adults. Abrysvo is the only one also approved for use during pregnancy to protect infants. Your doctor can help determine which option fits your situation, but the most important decision is simply whether to get vaccinated at all, not which brand to choose.